Trip systems are designed to respond to power faults detected in circuit breakers. Most simple trip systems employ an electromagnet to trip the circuit in response to short circuit or overload faults. The electromagnet provides a magnetic field in response to the current flowing through the breaker. When the current level increases beyond a predetermined threshold, the magnetic field "trips" a mechanism which causes a set of circuit breaker contacts to release, thereby "breaking" the circuit path.
Many simple trip systems also employ a slower responding bi-metallic strip, which is useful for detecting a more subtle overload fault. This is because the extent of the strip's deflection represents an accurate thermal history of the circuit breaker and, therefore, even slight current overloads. Generally, heat generated by the current overload will cause the bi-metallic strip to deflect into the tripping mechanism to break the circuit path.
The tripping systems discussed above are generally adequate for many simple circuit breaker applications, but there has been an increasing demand for a more intelligent and flexible tripping system. For example, many industries today include 3-phase power equipment that must be adjusted and monitored on a regular basis. Processor-based tripping systems have been developed to meet these needs.
Processor-based tripping systems typically indicate the status of the tripping system in an expensive and power inefficient manner. One known system, for example, employs a pop-up plunger to indicate certain types of trip causes. The pop-up plunger includes a solenoid mechanism that is not only expensive, but also requires an excessive amount of power.
Other systems use light emitting diodes (LEDs) to indicate the status of the tripping system. LEDs are less expensive than the pop-up plunger devices but, due to their power consumption, require a relatively expensive external power source.
Accordingly, in addition to providing flexibility to power distribution systems, processor-based tripping systems must also efficiently and reliably display their status in a cost effective manner.